1. Field of the Invention
The present invention relates to the field of cellular communication systems. More specifically, it relates to a device for establishing cells at a predetermined geographic site and for predicting the performance of the cells before an actual cellular system has been implemented at the site.
2. Description of the Related Art
A wireless, cellular telephone system is a large, complex communication network, characterized by multiple users roaming throughout an extensive coverage area while communicating with others within the same coverage area, or some other coverage area.
FIG. 1, for example, illustrates a typical geographic site 100 intended to receive a wireless infrastructure (e.g., antennas, repeaters, etc.) and become part of the communications network. The geographic site 100 has a length X and a width Y, where X and Y may form an area of e.g., one square mile. Within geographic site 100, a plurality of cells (e.g., four cells) are formed to provide wireless coverage within the site 100, as depicted in FIG. 2. The functions of the communication network, such as frequency reuse and handoff between coverage cells that allow the user to roam with a wireless telephone, are transparent to the user. The design of the cell layouts, and antenna placements, that ensure such seamless operation usually involve extensive, on-site measurements of signal strength versus distance from e.g., a system antenna, or complex electromagnetic modeling of the site, or some combination of these methods.
For example, electromagnetic modeling can be performed using a design aid such as the Wireless System Engineering (WiSE©)) computer-based tool. In order for such electromagnetic modeling to be useful, however, a lengthy checklist of data must be entered into the WiSE tool. For instance, the WiSE tool must be supplied with e.g., exact relative locations of walls, buildings, natural obstructions, etc. at the site 100 that might interfere with the transmission of signals within the site 100. In addition, the WiSE tool must be supplied with the material make-up of these objects so that a determination of the electromagnetic properties of the obstructions can be made. Once the WiSE tool has sufficient information, it can determine the optimum antenna location(s) at the site 100.
While the above described method is reliable, the collection of the critical data is very tedious. Moreover, problems often arise after the system has been installed due to sources of interference that were not considered or that did not exist during the information gathering (i.e., site examination) phase, or due to human error in measuring and/or estimating signal obstructions and/or material make-up. As a result, many problems associated with the modulation, data rates, or protocols of systems go undiscovered until the full system infrastructure is installed at a site. For example, holes (i.e., areas through which a signal is not being transmitted) in the coverage area due to e.g., incomplete surveys, can require costly additions or moves of system infrastructure. The costs associated with correcting these types of problems on site can be enormous and prohibitive. Thus, there exists a need for an apparatus and system for accurately predicting and evaluating cellular system performance before an actual cellular system is installed at a site.